Simplest way is to poison the thing and wait for it to die, but if the poison wears off or if it kills ya…..
I say, bring Null Dark, Null Light, Null Air, enough poisons and a Legion with Fig Gemsplosion or Aether Soulstone Gemsplosion.
Wait till he runs outta MP….deal some damage in between.
(P.S.: Using Black Hat for Dark defence, 2 moonstones for Light, one Steel Stole for Physical and one Wing Shield for Air [Partial], you might beat him, using Verhn, Legion and Mardek. The third chap is upto you. Make sure to apply DMG% defense, Degeneration 10%, most DMG% attack, Resist DARK, LIGHT -50%, Air -50%, etc, ie: all you need to defend against dark, light and air.)
Mardek can NullDark and Light.
If you want, take Sharla for NullAir.
Verhn must use Cursed Blade, Cursed Beret, Steel Stole and 2 Moonstone Rings. With this kind of resistance, all you have to worry about is Air.
Avoid Air or Light attacks, try to use Mardek and Verhn with BloodSword and Cursed Blade respectively. If all of Verhn’s Attack reactions are active, you’ll get a battle worth seeing.
Noxious Bomb ALWAYS causes poison unless target has resistance to it.
Poison won’t be completely effective unless the Demon’s Regen is destroyed.

Couldn’t it be as simple to use curse from Legion and then use Solaar’s viper claw like Arep said to poison him? Or is their something I’m missing about how curses work?
Edit: Turns out Curse doesn’t seem to work on Security Demon for whatever reason. Oh well.

Hey, do you like games? So do we — that’s what makes Kongregate the best source of free games online. We have thousands upon thousands of free online games, from both one-man indies and large studios, rated and filtered so you can play the best of the best. Read more »